Billions of cicadas set to emerge after 17 years underground

TIM PALMER: For 17 years they've waited underground, sucking on tree roots, readying for just this time when in their billions they will burst through the earth, enveloping half of the east coast of the United States in a deafening, screeching tide.

It could be a horror movie, right down to its name - Brood II. In fact, it's straight from the pages of natural history. Brood II is one of the biggest colonies of cicadas in the world. It will emerge over the next days and take wing for local trees in a wave that scientists say will outnumber the human population from North Carolina to Connecticut by 600 to one.

While scientists say Brood II is a big one, unlike a locust plague, the cicadas will do little damage to vegetation. They come to breed and lay eggs, which will hatch and then in no time at all, the brood will go back underground until 2030.

Jennifer Macey reports.

(sound of cicadas)

JENNIFER MACEY: Any day now on the east coast of the United States, this sound will intensify to ear-splitting proportions, as billions of cicadas emerge from the ground in a rare synchronised display of nature.

MICHAEL RAUPP: Oh there are going to be billions if not trillions of cicadas. We're gonna see birth, we're gonna see death, we're gonna see sex, we're gonna see romance.

JENNIFER MACEY: Dr Michael Raupp is an entomologist at the University of Maryland. He says these periodical cicadas are unique to the north eastern part of the US and rare in that they have the longest lifespan of all insects.

They live underground for 17 years.

MICHAEL RAUPP: They emerge simultaneously in such massive numbers that the predators that would like to eat them and will eat them can never eat enough that the population of these three species, and it is three species that emerge simultaneously, so some will survive. It's a very bizarre and crazy strategy, zany frankly.

JENNIFER MACEY: And while they can survive underground for 17 years, they spend a mere four weeks in the daylight before dying.

MICHAEL RAUPP: After the females and males hook it up in the tree tops, the females will move to the branches, they'll lay their eggs in the tips. The adults will then die and the little tiny eggs that they've inserted in the branches will emerge several weeks to a month thereafter. Then the tiny nymphs that hatch from those eggs will actually drop as much as 80 feet from the tree tops to the earth below, burrow underground and attach to the roots of the trees and feed again for another 17 years.

JENNIFER MACEY: And will they be noisy?

MICHAEL RAUPP: Oh they're going to be extremely noisy. This is a big boy band. It's only the male cicadas that sing, and their sound levels will approach about 90 decibels. This is the sound of a jet aircraft, a very loud lawnmower, or in this case, because these are just teenagers, they're 17 years old, it's about as loud as a rock concert.

JENNIFER MACEY: Australia's foremost cicada expert is Dr Max Moulds, a senior research fellow at the Australian Museum. He says there's nothing quite like it in Australia.

MAX MOULDS: No, we have no periodical cicadas that we know of. That means ones that are restricted to an exact lifecycle in time. Some of our large ones, the Green Grocers found along the east coast, Sydney, Melbourne, they will usually have a life cycle of about six years.

JENNIFER MACEY: While the cicadas may do some damage to fruit trees by laying eggs in the cracks of branches, they're not as devastating as a locust plague which eats everything in sight.

For scientists, they're a natural wonder. Professor Chris Simon from the University of Connecticut has been studying the different broods for a long time.

CHRIS SIMON: It's really spectacular. They start coming out in the evening and there's so many. If you sit quietly you can actually hear them walking over the leaf litter. And then they start crawling up on all the trees and you look around with a head lamp and they're just like white flowers 'cause they're white when they first come out.

JENNIFER MACEY: There are 15 separate broods of cicadas in North America. Each emerges at a different time, after either 13 or 17 years underground. That means in any given year, at least one brood appears somewhere in the north east of the continent.

Professor Simon says land clearing has already killed off some of the broods.

CHRIS SIMON: Ploughing up fields and building, you know, cementing over areas, just clearing out the forests, so the patches of cicadas are getting smaller and smaller over the years. When their populations become smaller and smaller then eventually they just go extinct.